In Syria, where the U.S. is leading an air campaign against Islamic State targets and Russian military advisors are arriving to help the Assad regime, the two militaries aren’t talking to each other.

“Coalition forces are focused on conducting counter-ISIL operations, and so to my knowledge there is no military-to-military contact at this point,” Air Force Col. Pat Ryder, spokesman for U.S. Central Command, told reporters Friday morning.

“We’re keeping an eye on the Russian situation there, but right now again there’s really no deconfliction to do,” Ryder said, answering a question about how U.S. and anti-ISIS coalition forces and the Russian military are keeping out of each other’s way in Syria. “I think what you’re getting at is: [deconfliction] in the event there’s some type of Russian military or air activity, but again, I’m not going to speculate or talk about hypotheticals. Certainly, we have very professional air forces, and the coalition is going to ensure the safety of those forces where we operate.”

Related: NATO Caught ‘Surprised’ By Russia’s Move Into Syria

But Russia’s military presence in Syria, at least, is no longer hypothetical. Just hours before Ryder’s press briefing, Russian Foreign Minister Sergei Lavrov confirmed that Moscow had sent troops and equipment to help its longtime client, Syrian leader Bashar al-Assad, fight ISIS. Lavrov declined to confirm a Reuters report that the Russian troops had seen combat, but he did warn the U.S. about a growing risk of “unintended incidents” if the countries’ militaries did not cooperate in Syria.

When Ryder was asked specifically about deconfliction between coalition and Russian forces, the Pentagon spokesman referred the question to the State Department. But State Department spokesman John Kirby tossed it right back: “You have to talk to DOD about air coordination over the skies of Syria. That is not a State Department function.”

Kirby did note that the Pentagon has “routine military-to-military exchanges and dialogue with Russia, just as a matter of course.”

And he said that while the U.S. is hardly coordinating the air campaign with Assad or his government, it is using back channels, such as the Syrian representative to the U.N., to notify Damascus of imminent actions.

“There’s no coordination with the air campaign and the Syrian regime, but yes, they have been notified in the past about air activity and advised to stay clear of it,” Kirby said.

James Stavridis, former Supreme Allied Commander at NATO and now dean of the Fletcher School of Law and Diplomacy at Tufts University, said the absence of military-to-military contact is troubling.

“It is very dangerous to have both Russian and U.S. troops in a confined battle space, essentially on opposite sides of a civil war, without contact for deconfliction of any combat or support activities,” Stavridis said. “Open communication at the strategic and tactical level are both important.”

Kirby noted that there are diplomatic channels for broader contact with Russia. “There are many vehicles through which we communicate with Russian leaders about their activities and their intentions,” he said, citing two phone calls between Lavrov and U.S. Secretary of State Kerry in the past week. The U.S. embassy in Moscow “routinely talks to Russian leaders and officials about all manner of issues, particularly those that are of concern to us,” he said.

“We’ll continue to keep the lines of communication open as we feel we need to to gain better clarity,” Kirby said. “While the intent isn’t perfectly clear, our concerns remain valid and we’re going to continue to have these discussions with Russian leaders going forward.”

Risk Is Growing

Lavrov blamed Washington for severing military ties after Russia annexed Crimea and invaded Ukraine, fracturing a “professional” relationship that had for years been “important for the avoidance of undesired, unintended incidents.”

“They understand each other very well,” he said of U.S. brass and their Russian counterparts. “If, as John Kerry has said many times, the United States wants those channels frozen, then be our guest.”

Meanwhile, the risk of “unintended incidents” between U.S. and coalition forces and Russian and Syrian government forces appears to be growing. The U.S. is deepening agreements with Turkey to use its bases and clear its border of ISIS fighters. It is also training and equipping Syrian fighters and reinserting them into the fight in Syria, where it has vowed to defend them against ISIS or Assad.

U.S. officials also say Moscow has stationed about 200 naval infantrymen near the Syrian city of Latakia, and has sent in SA-22 anti-aircraft missiles to be operated by Russians. Meanwhile, Lavrov confirmed that the Russian Navy is beginning exercises off the Syrian coast, home to its only Mediterranean naval base, at Tartous. At least five missile-armed ships will take part, Reuters reported.

Stavridis noted that the Soviet and U.S. navies shared detailed action plans during the Cold War to avoid accidental, escalatory interactions, and said this might serve as a model in the new conflict. “We will need similar dialogue, and possibly such protocols, to avoid incidents in Syria,” he said.

Russia’s latest moves caught the U.S. and NATO by surprise. “I know of no prior notice that was given to the United States with respect to these additional activities that Russia has taken,” the State Department’s Kirby said.

So what’s next? Kirby said later Friday that the U.S. opposes “any actions in Syria that empowers the regime to escalate the conflict.”

“We’d welcome constructive anti-ISIL efforts by Russia, but it can’t start with, and it can’t be a function of, continued support to the Assad regime,” Kirby said. He said Russia has not been asked to join the 60-plus nations now fighting ISIS, and added, “It wasn’t an implied invitation.”

But earlier in the day, White House spokesman Josh Earnest had seemed to suggest that the coalition’s door might be open to Moscow.

“Any efforts that anybody would take, including the Russians, to offer material support to the Assad regime would be counterproductive,” Earnest said in a briefing. “So at the same time, we would welcome constructive Russian contributions to our anti-ISIL campaign. There are more than 60 countries who are participating in that effort, and we would welcome constructive Russian support for those efforts.”

Stavridis agreed, saying, “Far better than sending troops to bolster the failing Assad regime would be Russian participation in the anti-Islamic State coalition alongside more than 40 nations who seek to destroy ISIL.”

Earnest said that the U.S. remains unsure about Russia’s intentions in Syria. (Critics say this inability to understand President Vladimir Putin prevented the Obama administration from anticipating the invasion of Ukraine, or responding effectively to the conflict that followed.)

“At this point, it’s hard to tell exactly what they’re planning to do,” he said. “We’ve, I think. tried to make clear what we would like to see them do, but ultimately they’ll have to decide.”

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